Lemon blueberry thyme is a deliciously fresh and flavorful cake that celebrates all things Spring. This cake is made with a zesty lemon cake that is studded fresh blueberries, and it's layered with a creamy lemon thyme buttercream.
Preheat the oven to 350℉. In a stand mixer bowl combine all the dry ingredients and sift or whisk them together to de-clump any flour and sugar. Place on the mixer with a paddle attachment and start the mixer on low speed.
Then add the room temperature butter cubes piece by piece into the dry ingredients. Allow the butter to incorporate into the dry mix. The mixture will look like sand when it's ready for the next step. This could take a few minutes at low speed.
Next, add the vanilla extract and eggs one at a time until incorporated. The batter will begin to smooth out. Now combine the lemon juice and milk together, the milk will start to curdle and use immediately. Pour the milk mixture into the batter and increase the mixer speed to medium to smooth out the cake batter. Keep mixing for one minute until it’s thick and creamy. Stop the mixer and scrape down the sides of the bowl to make sure everything is incorporated.
Then toss the fresh blueberries and 1 ½ teaspoon of ap flour. Stir the blueberries and lemon zest into the cake batter. Continue to fold until the blueberries are well distributed through the cake batter.
A single batch of this cake recipe makes enough for 3 – 6” cake layers or 2 – 8” cake layers. To prepare the cake pans, spray each pan with cooking or baking spray and then line the bottom of the pan with parchment paper. Place the parchment paper on top of the cooking spray to prevent the cake from sticking to the bottom of the pan.
To make 3 cake layers evenly pour or scoop the cake batter into the 3 pans (or weight out by using a baking scale). Place the cake pans into the preheated oven and bake for 30-35 minutes. Depending on how high or the size of the pan the baking time may vary.
After 35 minutes, carefully check the cakes with a toothpick. If the toothpick comes out clean, then the cakes are done, if not add additional time in 5-minute increments and recheck them.
Once the cakes are done baking, remove the cakes from the oven and set aside to cool. Allow to cool for 10 minutes, the cake pans should be cool enough to touch but still warm. Then carefully remove the cakes from the pan by turning the cakes upside and flip them back upright. Leave the parchment paper on the bottom to finish cooling. If the cakes are sticking to the cake pans, carefully run an off-set spatula or a small knife around the edges of the cake then flip the cakes out of the pan. That should release the cake from the sides of the pan.
After the cakes have almost cooled completely, wrap in plastic wrap and freeze for 30 minutes. At this stage, you can cover the cakes and leave them in the freezer for several days or up to a month before decorating them. I prefer to chill the cakes before decorating so they are easier to handle and decorate later.
To make the thyme butter, start with a medium pot on low heat. Add the unsalted butter and fresh thyme sprigs. Begin to melt the butter slowly but don’t allow it to boil. Once the butter is melted fully then turn off the heat and along the thyme to steep into the butter. After 30 minutes strain the thyme from the butter and place the strained thyme butter into the fridge to chill and harden.
To make the lemon gel start with a small pot. Whisk the lemon juice and cornstarch together. Bring to a boil while mixing continuously. After the lemon juice has thickened, remove from the heat and mix into the lemon zest. Let cool and set for 15 minutes.
In a stand mixer bowl, add the thyme butter and lemon gel. Mix on medium-high until the butter is light in color and fluffy. Stop the mixer every few minutes to scrape down the sides of the bowl to make sure all the butter is well blended. This step can take up to a few minutes.
Once the butter and lemon gel is light in color and fluffy, continue to mix on medium and add the vanilla extract, salt, and thyme leaves. Scrape down the sides of the bowl again before moving to the next step.
Then gradually add half of the sifted powdered sugar to the butter mixture. Next, add 1 ½ Tablespoon of milk. Scrape down the sides of the bowl and especially the center of the bowl to make sure all the powdered sugar is getting incorporated.
Finally, add the last half of the powdered sugar and mix on medium-high. Continue to mix and scrape down the sides of the bowl until you don't see any more powdered sugar. If the buttercream is a little stiff, then mix an additional 1½ tablespoon of milk if needed. Continue to mix until you have a creamy and smooth buttercream. The lemon thyme buttercream is ready to use.
Remove the chilled cakes from the freezer and carefully slice the top of any dome of the cakes off to make them level and flat. This makes the stacking process much more manageable. Or if the cakes come out flat, you don’t have to cut off the tops.
Next is decorating, use an offset spatula for layering the lemon thyme buttercream in between each cake layer. If the blueberries have sunk to the bottom of the cake (that’s okay), then flip the cakes upside down, so the blueberries are facing up. Continue to a crumb coat, so the whole cake is lightly covered then chill in the fridge for 20 minutes until the crumb coat has set.
After the crumb coat is chilled add a thicker layer of buttercream onto the cake for the final coat. This is where you make the edges straight and pretty. Place back into the fridge to set the final coat of frosting.
Then put the lemon thyme buttercream into a piping bag to create the swirls on top with a star tip. Then squeezing the piping bag and moving your wrist into a circle you will create the swirl. The goal is to pipe a circle on top of the previous circle until you have covered the top of the cake. Then add fresh blueberries on top of the swirls and a few thyme sprigs on the side to complete this delicious springtime cake.